[e-lang] FQN-based upgrade (was Re: scoping rules of when-catch)

[Kevin Reid]

On May 31, 2006, at 12:53, Mark S. Miller wrote:

> But for named objects, all of whose containing objects are named,  
> these must
> have fully qualified names that depend only on their package and  
> containing
> object names in the source code. This allows us to consider live- 
> upgrading old
> instances of such definitions to behave according to new  
> definitions. If we
> assigned FQNs automagically, these assignments would not be stable  
> enough for
> programmers to reason about upgrading old instances to instantiate  
> new behavior.

I have heard talk of FQN-based upgrade over the years but not seen  
any discussion of how it is to be done safely.

Since FQNs are strings, there must be some additional permission to  
allow upgrade; what form does it take? (A sibling-facet of an  
Evaluator?)

How is the fact that a DeepFrozen or transparent Selfless object must  
not be upgraded represented?

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>